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Fearon U, Hanlon MM, Floudas A, Veale DJ. Cellular metabolic adaptations in rheumatoid arthritis and their therapeutic implications. Nat Rev Rheumatol 2022; 18:398-414. [PMID: 35440762 DOI: 10.1038/s41584-022-00771-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/04/2022] [Indexed: 12/16/2022]
Abstract
Activation of endothelium and immune cells is fundamental to the initiation of autoimmune diseases such as rheumatoid arthritis (RA), and it results in trans-endothelial cell migration and synovial fibroblast proliferation, leading to joint destruction. In RA, the synovial microvasculature is highly dysregulated, resulting in inefficient oxygen perfusion to the synovium, which, along with the high metabolic demands of activated immune and stromal cells, leads to a profoundly hypoxic microenvironment. In inflamed joints, infiltrating immune cells and synovial resident cells have great requirements for energy and nutrients, and they adapt their metabolic profiles to generate sufficient energy to support their highly activated inflammatory states. This shift in metabolic capacity of synovial cells enables them to produce the essential building blocks to support their proliferation, activation and invasiveness. Furthermore, it results in the accumulation of metabolic intermediates and alteration of redox-sensitive pathways, affecting signalling pathways that further potentiate the inflammatory response. Importantly, the inflamed synovium is a multicellular tissue, with cells differing in their metabolic requirements depending on complex cell-cell interactions, nutrient supply, metabolic intermediates and transcriptional regulation. Therefore, understanding the complex interplay between metabolic and inflammatory pathways in synovial cells in RA will provide insight into the underlying mechanisms of disease pathogenesis.
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Affiliation(s)
- Ursula Fearon
- Molecular Rheumatology, Trinity Biomedical Sciences Institute, TCD, Dublin, Ireland. .,EULAR Centre of Excellence, Centre for Arthritis and Rheumatic Diseases, St Vincent's University Hospital, Dublin, Ireland.
| | - Megan M Hanlon
- Molecular Rheumatology, Trinity Biomedical Sciences Institute, TCD, Dublin, Ireland.,EULAR Centre of Excellence, Centre for Arthritis and Rheumatic Diseases, St Vincent's University Hospital, Dublin, Ireland
| | - Achilleas Floudas
- Molecular Rheumatology, Trinity Biomedical Sciences Institute, TCD, Dublin, Ireland.,EULAR Centre of Excellence, Centre for Arthritis and Rheumatic Diseases, St Vincent's University Hospital, Dublin, Ireland
| | - Douglas J Veale
- EULAR Centre of Excellence, Centre for Arthritis and Rheumatic Diseases, St Vincent's University Hospital, Dublin, Ireland
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Floudas A, Gorman A, Neto N, Monaghan MG, Elliott Z, Fearon U, Marzaioli V. Inside the Joint of Inflammatory Arthritis Patients: Handling and Processing of Synovial Tissue Biopsies for High Throughput Analysis. Front Med (Lausanne) 2022; 9:830998. [PMID: 35372383 PMCID: PMC8967180 DOI: 10.3389/fmed.2022.830998] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2021] [Accepted: 02/04/2022] [Indexed: 11/16/2022] Open
Abstract
Inflammatory arthritis is a chronic systemic autoimmune disease of unknown etiology, which affects the joints. If untreated, these diseases can have a detrimental effect on the patient's quality of life, leading to disabilities, and therefore, exhibit a significant socioeconomic impact and burden. While studies of immune cell populations in arthritis patient's peripheral blood have been informative regarding potential immune cell dysfunction and possible patient stratification, there are considerable limitations in identifying the early events that lead to synovial inflammation. The joint, as the site of inflammation and the local microenvironment, exhibit unique characteristics that contribute to disease pathogenesis. Understanding the contribution of immune and stromal cell interactions within the inflamed joint has been met with several technical challenges. Additionally, the limited availability of synovial tissue biopsies is a key incentive for the utilization of high-throughput techniques in order to maximize information gain. This review aims to provide an overview of key methods and novel techniques that are used in the handling, processing and analysis of synovial tissue biopsies and the potential synergy between these techniques. Herein, we describe the utilization of high dimensionality flow cytometric analysis, single cell RNA sequencing, ex vivo functional assays and non-intrusive metabolic characterization of synovial cells on a single cell level based on fluorescent lifetime imaging microscopy. Additionally, we recommend important points of consideration regarding the effect of different storage and handling techniques on downstream analysis of synovial tissue samples. The introduction of new powerful techniques in the study of synovial tissue inflammation, brings new challenges but importantly, significant opportunities. Implementation of novel approaches will accelerate our path toward understanding of the mechanisms involved in the pathogenesis of inflammatory arthritis and lead to the identification of new avenues of therapeutic intervention.
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Affiliation(s)
- Achilleas Floudas
- Molecular Rheumatology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin, Ireland
- European League Against Rheumatism (EULAR) Centre of Excellence, Centre for Arthritis and Rheumatic Diseases, St. Vincent's University Hospital, University College Dublin (UCD), Dublin, Ireland
- *Correspondence: Achilleas Floudas
| | - Aine Gorman
- European League Against Rheumatism (EULAR) Centre of Excellence, Centre for Arthritis and Rheumatic Diseases, St. Vincent's University Hospital, University College Dublin (UCD), Dublin, Ireland
| | - Nuno Neto
- Trinity Centre for Biomedical Engineering, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin, Ireland
| | - Michael G. Monaghan
- Trinity Centre for Biomedical Engineering, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin, Ireland
| | - Zoe Elliott
- European League Against Rheumatism (EULAR) Centre of Excellence, Centre for Arthritis and Rheumatic Diseases, St. Vincent's University Hospital, University College Dublin (UCD), Dublin, Ireland
| | - Ursula Fearon
- Molecular Rheumatology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin, Ireland
- European League Against Rheumatism (EULAR) Centre of Excellence, Centre for Arthritis and Rheumatic Diseases, St. Vincent's University Hospital, University College Dublin (UCD), Dublin, Ireland
| | - Viviana Marzaioli
- Molecular Rheumatology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin, Ireland
- European League Against Rheumatism (EULAR) Centre of Excellence, Centre for Arthritis and Rheumatic Diseases, St. Vincent's University Hospital, University College Dublin (UCD), Dublin, Ireland
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